The invention relates to improvements in spacer frames (also called spacers) which can be used between marginal portions of spaced-apart panes in so-called double windows or multiple-pane windows or analogous shatter-, bullet- or soundproof or thermally insulating laminates. More particularly, the invention relates to improvements in methods of and in apparatus for making holes in whose portions or walls of hollow spacer frames which are disposed between a supply of flowable desiccant in the interior of a frame and the space between the spaced-apart panes of a multiple-pane window or the like.
It is necessary to provide the hollow spacer frame of a multiple-pane window or a similar laminate with a plurality of holes (e.g., small perforations) which ensure that moisture in the space between the panes can escape into the interior of the frame to be absorbed by granular, pulverulent or other particulate desiccant in the interior of the frame. German Utility Model No. 74 26 966 of VAW-Leichtmetal GmbH discloses a spacer frame wherein the wall between the supply of confined desiccant and the space between the window panes is provided with pairs of neighboring elongated parallel slits. Strips of material between the slits of each pair are depressed toward the interior of the hollow frame in order to enlarge the paths for the flow of vapors from the space toward contact with the desiccant. If necessary, some of the strips are thereupon pressed inwardly to reduce the cross-sectional areas of the respective paths, i.e., to prevent penetration of particles of flowable desiccant into the space which is surrounded by the frame and is flanked by the two panes. A drawback of the frame which is described in the Utility Model is that finely comminuted desiccant which is located above the space between the panes (i.e., which is confined in the spacer frame along the upper edge of a multiple-pane window) is likely to seep through the slits in the adjacent portion of the wall and to penetrate into the space to detract from the appearance of the window. Some finely comminuted desiccant is bound to be found in the interior of the spacer frame, mainly because the frame is normally made (or is often made) by bending a straight tubular desiccant-containing blank of ductile metallic material in order to convert the blank into a square, rectangular or otherwise configurated frame. Such bending (reference may be had to commonly owned U.S. Pat. Nos. 4,627,263 and 4,912,837) invariably entails comminution of certain granulae of desiccant so that the thus obtained fine powder is likely to penetrate into the space between the panes under the action of gravity. Shaking and/or other movements of the panes during assembly with the frame promote the escape of finely comminuted desiccant into the space which is surrounded by the spacer frame. Moreover, if the multiple-pane laminate is used as a window in a motor vehicle, vibrations of the panes while the vehicle is in motion also promote penetration of finely comminuted desiccant into the aforementioned space. Still further, desiccant which is confined in the spacer frame of a multiple-pane window in a motor vehicle is likely to escape from the interior of the frame during raising or lowering of the window, under the action of wind, as a result of banging on the window or due to a combination of such influences.
German Utility Model No. 79 25 919 of Mannesmann AG discloses a spacer frame wherein the wall which separates the space between the panes from the confined supply of desiccant is formed with outwardly extending protuberances surrounding circular or slot-shaped passages for the flow of vapors from the space toward contact with the supply of desiccant. The protuberances have ragged edges which surround the passages. These passages permit finely comminuted particles of desiccant to penetrate into the space and to thus adversely affect the appearance of the laminate (such as a multiple-pane window) in which the spacer frame is put to use.
U.S. Pat. No. 3,865,144 to Westhoff discloses a spacer frame wherein the wall which separates the space between the panes from the supply of confined desiccant is formed with longitudinally extending slots and the material of the wall next to each slot is depressed through an acute angle to extend into the interior of the frame and to establish a relatively wide path for the flow of vapors toward contact with the particles of desiccant. Such slots are highly likely to permit penetration of finely comminuted desiccant into the space between the panes.
Published German patent application No. 26 06 387 of Poignon discloses a spacer frame having an elongated weakened portion which can be readily destroyed to establish a path for the flow of vapors from the space between two panes into contact with the supply of confined desiccant. This publication proposes to split the weakened portion in the region of the web to thus provide a long path for vapors. Such elongated path weakens the frame and permits escape of finely comminuted desiccant into the space between the panes.
The aforementioned commonly owned U.S. Pat. No. 4,627,263 also discloses a spacer frame having a wall with a weakened portion which is provided with perforations enabling confined desiccant to attract moisture from the space between the panes. This patent deals primarily with conversion of tubular blanks into polygonal frames and with expulsion of some desiccant from the bent corner portions of the converted blanks.